Editing Geocentric orbit (section)

==Types==
The following is a list of different geocentric orbit classifications.

===Altitude classifications===
[[Image:Orbits around earth scale diagram.svg|thumb|Low (cyan) and Medium (yellow) Earth orbit regions to scale. The black dashed line is the geosynchronous orbit. The green dashed line is the 20,230 km orbit used for [[Global Positioning System|GPS]] satellites.]]
{{anchor|Altitude}}
; [[Transatmospheric orbit]] (TAO): Geocentric orbits with altitudes at [[apogee]] higher than {{cvt|100|km|mi}} and [[perigee]] that intersects with the [[Kármán line|defined atmosphere]].<ref>{{Cite web |last=McDowell |first=Jonathan |date=24 May 1998 |title=Jonathan's Space Report |url=https://planet4589.org/space/jsr/back/news.361.txt |quote=Transatmospheric orbit (TAO): orbital flight with perigee less than 80 km but  more than zero. Potentially used by aerobraking missions and transatmospheric vehicles, also in some temporary phases of orbital flight (e.g. STS pre OMS-2, some failures when no apogee restart)}}</ref>
; [[Low Earth orbit]] (LEO) : Geocentric orbits ranging in altitude from {{cvt|160|km|mi|sigfig=1}} to {{cvt|2,000|km|mi}} above [[mean sea level]]. At 160 km, one revolution takes approximately 90 minutes, and the circular orbital speed is {{cvt|8|km/s|ft/s}}.
; [[Medium Earth orbit]] (MEO) : Geocentric orbits with altitudes at apogee ranging between {{cvt|2,000|km|mi}} and that of the [[geosynchronous orbit]] at {{cvt|35,786|km|mi}}.
; [[Geosynchronous orbit]] (GSO): Geocentric circular orbit with an altitude of {{cvt|35,786|km|mi}}.  The period of the orbit equals one [[sidereal day]], coinciding with the rotation period of the Earth. The speed is approximately {{cvt|3|km/s|ft/s}}.
; [[High Earth orbit]] (HEO) : Geocentric orbits with altitudes at apogee higher than that of the geosynchronous orbit. A special case of high Earth orbit is the [[highly elliptical orbit]], where altitude at perigee is less than {{cvt|2,000|km|mi}}.<ref name="nasa">[http://gcmd.nasa.gov/User/suppguide/platforms/orbit.html Definitions of geocentric orbits from the Goddard Space Flight Center] {{webarchive |url=https://web.archive.org/web/20100527132541/http://gcmd.nasa.gov/User/suppguide/platforms/orbit.html |date=May 27, 2010 }}</ref>

===Inclination classifications===
; [[Inclined orbit]] : An orbit whose [[inclination]] in reference to the [[equatorial plane]] is not 0.
:; [[Polar orbit]] : A satellite that passes above or nearly above both poles of the planet on each revolution. Therefore it has an inclination of (or very close to) 90 [[degree (angle)|degree]]s.
:; [[Sun-synchronous orbit|Polar Sun synchronous orbit]] : A nearly [[polar orbit]] that passes the [[equator]] at the same local time on every [[pass (spaceflight)|pass]]. Useful for image-taking satellites because shadows will be the same on every pass.

===Eccentricity classifications===
; [[Circular orbit]] : An orbit that has an [[Orbital eccentricity|eccentricity]] of 0 and whose path traces a circle.
; [[Elliptic orbit]] : An orbit with an [[Orbital eccentricity|eccentricity]] greater than 0 and less than 1 whose orbit traces the path of an [[ellipse]].
:; [[Hohmann transfer orbit]] : An orbital maneuver that moves a spacecraft from one [[circular orbit]] to another using two engine [[impulse (physics)|impulse]]s. This maneuver was named after [[Walter Hohmann]].
:; [[Geosynchronous transfer orbit]] (GTO) : A geocentric-[[elliptic orbit]] where the [[perigee]] is at the altitude of a [[low Earth Orbit]] (LEO) and the [[apogee]] at the altitude of a [[geosynchronous orbit]].
:; [[Highly elliptical orbit]] (HEO) : Geocentric orbit with apogee above 35,786 km and low perigee (about 1,000 km) that result in long dwell times near apogee.
::; [[Molniya orbit]] : A [[highly elliptical orbit]] with [[inclination]] of 63.4° and [[orbital period]] of ½ of a [[sidereal day]] (roughly 12 hours). Such a satellite spends most of its time over a designated area of the Earth.
::; [[Tundra orbit]] : A [[highly elliptical orbit]] with [[inclination]] of 63.4° and [[orbital period]] of one [[sidereal day]] (roughly 24 hours). Such a satellite spends most of its time over a designated area of the Earth.
; [[Hyperbolic trajectory]] : An "orbit" with eccentricity greater than 1. The object's [[velocity]] reaches some value in excess of the [[escape velocity]], therefore it will escape the gravitational pull of the Earth and continue to travel [[infinitely]] with a velocity (relative to Earth) decelerating to some finite value, known as the [[hyperbolic excess velocity]].
:; Escape Trajectory : This trajectory must be used to launch an interplanetary probe away from Earth, because the excess over escape velocity is what changes its [[heliocentric orbit]] from that of Earth.
:; Capture Trajectory : This is the mirror image of the escape trajectory; an object traveling with sufficient speed, not aimed directly at Earth, will move toward it and accelerate. In the absence of a decelerating engine impulse to put it into orbit, it will follow the escape trajectory after periapsis.
; [[Parabolic trajectory]] : An "orbit" with eccentricity exactly equal to 1. The object's [[velocity]] equals the [[escape velocity]], therefore it will escape the gravitational pull of the Earth and continue to travel with a velocity (relative to Earth) decelerating to 0. A spacecraft launched from Earth with this velocity would travel some distance away from it, but follow it around the Sun in the same [[heliocentric orbit]]. It is possible, but not likely that an object approaching Earth could follow a parabolic capture trajectory, but speed and direction would have to be precise.

===Directional classifications===
; [[Prograde orbit]] : an orbit in which the projection of the object onto the equatorial plane revolves about the Earth in the same direction as the rotation of the Earth.
; [[Retrograde orbit]] : an orbit in which the projection of the object onto the equatorial plane revolves about the Earth in the direction opposite that of the rotation of the Earth.

===Geosynchronous classifications===
; [[Semi-synchronous orbit]] (SSO) : An orbit with an altitude of approximately {{convert|20,200|km|mi|abbr=on}} and an [[orbital period]] of approximately 12 hours
; [[Geosynchronous orbit]] (GEO) : Orbits with an altitude of approximately {{convert|35,786|km|mi|abbr=on}}. Such a satellite would trace an [[analemma]] (figure 8) in the sky.
:; [[Geostationary orbit]] (GSO) : A [[geosynchronous orbit]] with an [[inclination]] of zero. To an observer on the ground this satellite would appear as a fixed point in the sky.
:; [[Clarke orbit]] : Another name for a geostationary orbit. Named after the writer [[Arthur C. Clarke]].
::; Earth orbital [[libration points]] : The [[libration points]] for objects orbiting Earth are at 105 degrees west and 75 degrees east. More than 160 satellites are gathered at these two points.<ref>[https://news.yahoo.com/s/space/20100503/sc_space/outofcontrolsatellitethreatensothernearbyspacecraft Out-of-Control Satellite Threatens Other Nearby Spacecraft], by Peter B. de Selding, SPACE.com, 5/3/10. {{webarchive |url=https://web.archive.org/web/20100505183446/http://news.yahoo.com/s/space/20100503/sc_space/outofcontrolsatellitethreatensothernearbyspacecraft |date=May 5, 2010 }}</ref>
:; [[Supersynchronous orbit]] : A disposal / storage orbit above GSO/GEO. Satellites will drift west.
:; [[Subsynchronous orbit]] : A drift orbit close to but below GSO/GEO. Satellites will drift east.
:; [[Graveyard orbit]], disposal orbit, junk orbit : An orbit a few hundred kilometers above [[geosynchronous]] that satellites are moved into at the end of their operation.

===Special classifications===
; [[Sun-synchronous orbit]] : An orbit which combines altitude and [[inclination]] in such a way that the satellite passes over any given point of the [[planet]]'s surface at the same local [[solar time]]. Such an orbit can place a satellite in constant sunlight and is useful for imaging, [[spy satellite|spy]], and [[weather satellite]]s.
; [[Moon orbit]] : The [[Orbital parameters|orbital characteristics]] of Earth's Moon. Average altitude of {{convert|384,403|km|mi}}, [[elliptical orbit|elliptical]]&ndash;[[inclined orbit]].

===Non-geocentric classifications===
; [[Horseshoe orbit]] : An orbit that appears to a ground observer to be orbiting a planet but is actually in [[Co-orbital satellite|co-orbit]] with it. See asteroids [[3753 Cruithne|3753]] (Cruithne) and [[2002 AA29|2002 AA<sub>29</sub>]].
; [[Sub-orbital spaceflight | Sub-orbital flight]] : A launch where a [[spacecraft]] approaches the height of orbit but lacks the [[velocity]] to sustain it.

<!--

;[[Retrograde orbit]]
;[[Decaying orbit]] : See [[orbital decay]].

-->
{{earth orbits}}